The present invention relates to a pressurized-water coolant nuclear reactor power plant installation of the type having a reactor pressure vessel, in which the fuel elements are located, and enclosed by a steel containment enclosure in the form of a large sphere which is air-tight, and which is itself enclosed by a secondary enclosure in the form of a concrete construction having a hemispherical top and a cylindrical side wall. The reactor core in the vessel includes a relatively large number of these fuel elements which must be replaced as their fuel becomes burned-up.
The elements in the central portion of the core become burned up first, and when this occurs, the pressure vessel's cover is removed, the central core elements are removed and the elements outside of this central core zone are shuffled inwardly and replaced by an off-site shipment of elements, usually comprising about one-third of the total core change.
For the above purpose, such an installation must include a fuel element storage pool where the fuel elements can be stored during the fuel element shuffling procedure, this requiring the pool to have a capacity for the storage of at least one complete off-site shipment of fuel elements. Preferably the storage pool should have a capacity for storing enough fuel elements for a complete charge of the elements in the reactor core, or in other words a full reactor charge of elements. The pool must be kept flooded with water and contain a fuel element rack interspacing the stored fuel elements far enough apart to exceed the critical distance between them. The pool must, of course, be enclosed in an air-tight manner.
Heretofore this fuel element storage pool has been located inside of the spherical steel containment enclosure and the latter has been required to be of a size to enclose not only the reactor vessel, and the other power plant components of the installation, such as the steam generators, coolant pumps and the like, but also the storage pool and its components.
The construction cost of the steel containment vessel is high in all events, it being spherical to provide strength against internal fluid pressure and being necessarily fabricated from steel plates. Anything that can be done to reduce its size, and therefore expense, is very desirable. At the same time, the provision of a separate storage pool building outside of the concrete secondary containment enclosure, which might permit such a size reduction, is undesirable because of the long transport distances between the pressure vessel and the storage pool and the requirement that the pool be enclosed in an air-tight manner, this involving substantial construction costs.
The object of the present invention is to effect a reduction in the necessary size of the steel containment enclosure without requiring the need for such an outside separate building with its described aspects.